Classic galactosemia has failed to be adequately treated by dietary restrictions of galactose with resiling long-term serious complications. We are now challenged to understand this enigmatic disorder and to solve the dilemma of how to adequately provide therapy for affected patients. This proposal encompasses a broad spectrum of research into the basic biochemical and genetic abnormalities in patients with deficiency of galactose-1-phosphate uridyltransferase. It presents a concerted effort to wed both basic and clinical investigation. It presents the potential for application of new techniques and experimental approaches. It responds to a mandate for targeting a vigorous research effort to understand the pathobiochemistry and molecular genetic basis for galactosemia and to utilize the results to develop new therapeutic strategies. To answer athe enigma of galactosemia the program consists for four projects supported by two cores.